A novel biomass-based NOB-rich porous carbon self-assembled into crosslinked 3D layered structures for supercapacitors

Abstract

The increasing demand for sustainable energy storage solutions highlights the necessity of exploring renewable biomass materials as supercapacitor electrodes. Tamarindus indica L. (TIL) nuclei are often considered agricultural waste. Their use as electrode materials reduces waste and generates economic value. In this study, a strategy to enhance the self-assembly of TIL and H₃BO₃ by (NH₄)₂C₂O₄ under hydrothermal conditions was proposed, and the B/N/O co-doped cross-linked 3D layered porous carbon materials were successfully constructed. In this process, (NH₄)₂C₂O₄ not only acts as a nitrogen- and oxygen-enriched precursor but also stabilizes the structure during self-assembly via (NH₄)₂C₂O₄ via electrostatic adsorption and hydrogen bonding. This results in the simultaneous formation of layered pores and doped heteroatoms during pyrolysis. Subsequently, KOH disrupts and recombines the connections between carbon layers, ultimately forming a three-dimensional cross-linked layered structure. The resulting carbon materials demonstrate exceptional properties, including a heteroatom content of 16.23–20.06 at.%, a specific capacitance of 367 F g⁻¹ at 0.5 A g⁻¹, and a capacitance retention of 97.69 % after 10,000 cycles. The symmetrical supercapacitor maintains 92.3 % cycling stability after 10,000 cycles. Density Functional Theoretical (DFT) calculations show that high levels of N/B/O doping and fringing B, N, and oxygen-containing groups enhance their ability to adsorb and store electrolyte ions. Using a two-dimensional (2D) layered structure as a precursor enables morphological control through KOH etching and provides new insights for developing high-performance biomass-derived electrodes.